130 EXPLOITATION OF PLANTS 
tion; and Naaninga, Welter and Bernard (4), working 
in Java at the Government Proefstation voor Thee. 
To these should be added Kozai, a Japanese investigator, 
whose work has been already quoted. 
The work of these chemists (and notably the British 
representatives) has shown that the most important 
change taking place in the fermentation process is in 
regard to the tannin. This substance becomes slightly 
oxidised, forming brown-coloured products which 
unite with the caffeine present; the significance of 
spreading the leaf in thin layers on the fermenting floor, 
and arranging for free access of air, is therefore at once 
clear. Further, it has been demonstrated that the colour 
and body of an infusion of tea depend upon the propor- 
tion of tannin oxidised ; the more complete the oxidation 
(“ fermentation”) the more colour and body. But 
the consumer demands a certain pungency in addition 
to these qualities, and pungency depends upon the 
relative amount of tannin left unoxidised. Here it is 
that the skill and experience of the practical planter 
comes in to decide how far the fermentation is to be 
allowed to go. During the process the leaf assumes a 
fine copper tint, and the characteristic odour of tea is 
developed; these are the criteria upon which the 
planter’s judgment is based. 
The main object of the fermentation would thus 
appear to be the oxidation of the tannin, Another 
change of much practical significance, and already hinted 
at, also takes place, and will be referred to below. 
The actual mechanism of the oxidation process has 
given rise to much discussion, and there have been the 
three inevitable theories. Bamber, in 1893, put forward 
